1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of Related Art
Image forming apparatuses that can perform duplex printing such as printers and copiers have been provided.
In duplex printing, it is required to precisely align the image forming positions in the front and back sides. In particular, when a sheet is trimmed after duplex printing, a misalignment between the front and back image forming positions may result in a failure in which the image on either side is partly lost in the edge part thereof after the trimming.
To cope with the problem, a duplex alignment function by using a dedicated chart has been proposed (e.g. see JP 2014-22919A). Specifically, the distance from the edge of a sheet to a duplex alignment mark of the dedicated chart is measured in each side, and the front and back image forming positions are aligned with each other. However, this technique requires outputting the dedicated chart on a sheet, and a waste sheet is therefore produced in every alignment.
On the other hand, a function of forming trim marks for an input image has been proposed (e.g. JP 2011-11367A). A possible strategy of eliminating a waste sheet is to utilize such trim marks for the duplex alignment.